To investigate intracellular interactions between oncogenic and non-oncogenic viruses in vitro. To investigate alteration of antigenic composition of tumor cell membranes by infection with non-oncogenic viruses. To investigate use of tumor cells with altered membrane antigenic profiles in immunotherapy and prophylactic vaccination. To investigate the effect of chemotherapeutic agents on RNA tumor virus replication in vitro. To determine by in vitro techniques the mechanism of action and optimal treatment schedules of various immune enhancer drugs for application to the treatment of neoplasms.